The present invention relates to a plastic cap having a sleeve which is inserted and secured in the filler spout of a fuel tank. Traditionally, filler spouts found on cars and trucks provide a cap with screw threads. The cap can be screwed on and off when fueling of the vehicle is required. Since the cap lies loose while fueling takes place, the opportunity arises for the cap to be misplaced, lost, or dropped to roll to a resting place from which it may be difficult to retrieve. Often, if fuel enters the spout too rapidly, it will splash or foam back on the hands, feet, or clothing of the person fueling the vehicle.
Various approaches have been taken in the prior art to solve the problems presented. Attempts at solutions are shown in the following patents which relate primarily to fuel tank covers: U.S. Pat. Nos. 1,902,456, 3,478,922, 3,903,942, 4,135,404, and 4,441,533. Other cover arrangements in the closure art generally are shown in U.S. Pat. Nos. 3,419,198, 3,465,925, and 4,106,656.